Many sportsmen, for example divers and cyclists, and drivers of vehicles such as snowmobiles, find it desirable to know what is happening behind them but cannot readily look over their shoulder as this means taking their eyes off events in front of them. In a fast moving sports such as cycling this can be extremely dangerous.
Proposals for mirrors that mount on the hand or wrist have been made, these mirrors being configured and positioned to provide a rear view. The major problem with the known devices is that they either provide too limited a field of vision or are bulky and awkward to use. In some instances their water drag or wind resistance mitigates against their use.